Molding compositions containing cellulosic filler and method of making



Unite MQLDING COMPUSITIONS C(JNTAINING CELLU- LUSIC FELLER AND METHGD FMAKING John A. Yourtee, Fredericksburg, Va., assignor to AmericanViscose Corporation, Philadelphia, Pa., a corporation of Delaware NoDrawing. Application July 31, 1953, Serial No. 371,715

17 (Iiaims. (Cl. 260-45) sisting of regenerated cellulose with a liquidcomprising a thermosetting aminoplast resin-forming condensate, and thendrying the mass and reducing it to a powder, yield molded objects whichare more translucent than objects molded from compositions containing afiller other than regenerated cellulose. However, in practice,considerable difiiculty is encountered when it is attempted to dry theliquid-treated regenerated cellulose because the regenerated celluloseis comparatively non-porous and does not completely absorb or take upthe liquid regardless of whether the latter is in a viscous, or in amobile; relatively non-viscous condition, at the time it is mixed withthe filler. For example, when regenerated cellulose sheet or othermaterial in the form of chips or clippings is treated with a thinlymobile solution of a potential resinforming urea-formaldehyde reactionproduct, the solution is not completely nor uniformly absorbed by anddistributed with respect to the filler, and liquid tends to drip out ofthe mass during drying thereof, which complicates the drying operation.In addition, objects molded from the compositions are brittle and haverelatively low strength.

Even more difiiculty is encountered if the filler consists ofregenerated cellulose powder. The addition of the thermosettingcondensate solution to the powder produces a soupy paste which isdiflicult to dry by the col.- ventional equipment adapted to dryingmolding compositions. Such pastes require drying in pans with stirringof the mass during the drying operation. Additionally, the use ofregenerated cellulose powder as sole filler for the molding compositionhas the elfect of reducing the translucency of the molded article ascompared to the translucency of objects molded from compositionscontaining a filler consisting of clippings or fragments of regeneratedcellulose.

One object of this invention is to provide a filler for thermosettingaminoplast molding compositions which, when impregnated with theresin-forming condensate, with or without a solvent, or with a solutionof the resinforming constituents, completely and uniformly absorbs theliquid to form an impregnated fibrous mass which holds the liquid, inthe proportion usually employed, without dripping, thus facilitatingdrying of the composition by conventional drying equipment. Anotherobject is to provide compositions which can be molded to providestronger, non-brittle objects having a translucence approaching that ofobjects molded from compositions comprising a filler consisting ofregenerated cellulose, and characterized by a uniform appearance. Afurther object is to provide a filler, which after impregnation with theresin-forming material, comprises a mass which can be dried rapidly andefficiently, by conventional drying equip ment without dripping of theliquid out of the mass, or

States Patent lQQ such seepage of the liquid within the mass as wouldresult in non-uniform distribution of the condensate in the driedproduct.

These and other objects of the invention are attained by impregnating afiller comprising a mixture of from 10 to 50, preferably about 35, partsof alpha-cellulose, preferably purified alpha-cellulose, and from 50 to90, preferably about 65, parts of a substance selected from the groupconsisting of regenerated cellulose water-insoluble, alkali-solublecellulose ethers and mixtures of two or more members of the group, inany form with a liquid or syrupy thermosetting aminoplast resincondensate in the presence or absence of a solvent, or with the liquidresin-forming constituents, to obtain a mass which after drying at atemperature below the temperature at which the condensate is convertedto the infusible, thermoset condition, comprises the filler and the dry,fusible condensate. The mass may then be ground to produce a moldingpowder. For example, the dried material may be reduced to the desiredparticle size and density by grinding it in a ball mill, roller mill, ora hammer mill, or by subjecting it to the action of a cutter, and duringsuch grinding or cutting various molding lubricants such as zincstearate, and/ or various coloring materials, curing catalysts, etc. maybe incorporated with it.

The term alpha-cellulose is meant to include cotton and commercialgrades of wood pulp as well as other forms of alpha-cellulose of equalor gerater purity derived from these or other sources.

It is preferred to mix the alpha-cellulose with a regenerated celluloseor cellulose ether having a high D. I. (degree of polymerization) i. e.,a cellulose which has not been severely degraded, for example, celluloseregenerated from a viscose which has been aged for a time less than tthe normal aging period, required to produce a viscose having the normalsalt (sodium chloride) test value of between 4 and 6, celluloseregenerated from nitrocellulose, or a cellulose ether which has not beensubjected to severe hydrolyzing conditions, since the less degradedregenerated cellulose or cellulose ether results in greater strength inobjects molded from the molding compositions.

The term water-insoluble, alkali-soluble cellulose ether is intended toinclude such ethers which are insoluble in water but soluble in aqueousalkali solutions of from 1 to 8% concentration at room temperature or atreduced temperature, including simple alkyl ethers (e. g. methyl andethyl celluloses), carboxyalkyl ethers (e. g. carboxymethyl cellulose),hydroxyalkyl ethers (e. g. hydroxyethyl cellulose), mixed alkyl,hydroxyalkyl ethers (e. g. methyl, hydroxyethyl) cellulose, and ethyl,hydroxyethel cellulose), mixed alkyl, carboxyalkyl ethers (e. g. methyl,carboxymethyl cellulose and ethyl, carboxymethyl cellulose), and thesalts of the carboxyalkyl ethers, especially those mentioned above,which contain free hydroxyl groups. The water-insoluble, alkali-solublecellulose ether may be one which is swellable in water but insolubletherein.

The compositions may be prepared by any of the methods known in the art.For example, the resin-forming syrup may be prepared first, and thefiller impregnated with the syrup in a separate operation, or theresin-forming condensate may be formed in situ in the filler bycombining or impregnating the filler with the resin-forming constituentsin liquid condition.

The temperature at which the mass is dried may vary and will depend uponthe particular thermosetting resinforming condensate or constituentsemployed. If. the filler is impregnated with a'con densate formed in aseparate step, the condensation may be advanced during the dryingbut thetemperature is controlled so that the resin is not brought to theinfusible state.

It the filler is impregnated with the liquid resin-forming constituents,or a solution thereof, the condensate is formed in situ in the massduring the drying. In any case, the product comprises the fillerimpregnated or combined with the resin-forming condensate which isconverted to the fully condensed, thermoset condition during subsequentmold- :mg or shaping operations performed under heat and pressure.

In addition to the mixture of alpha-cellulose and regenerated celluloseor cellulose ether, the molding composition may contain a minorproportion of one or more other fillers, such as wood flour, asbestos,cotton linters, clay, etc. Coloring materials, such as pigments anddyes, a mold lubricant, a plasticizing agent, other impregnating agents,and a curing catalyst, may be included during the processing, if desiredor necessary. In some applications, it may be desirable to include smallamounts of one or more modifying agents such as starches, gums,alginates, casein, etc.

The molding compositions of the invention have important advantages ascompared to molding compositions in which the filler consists entirelyof regenerated cellulose, while retaining to a large degree thedesirable characteristics of such all-regenerated cellulose filledcompositions, as a result of the conjoint use of the alphacellulose andregenerated cellulose or cellulose ether, both the alpha-cellulose andthe regenerated cellulose or ether contributing unique properties to thenew compositions. As compared to the all-regenerated cellulose filledcompositions, the advantages or improvements reside in better absorptionof the liquid comprising the resin-forming material, whereby dripping ofthe liquid is eliminated and drying is facilitated; and improvedstrength and toughness such that articles formed from the compositionscan be drilled or otherwise machined with less likelihood of chipping orcracking. For instance, clean holes may be drilled in buttons or thelike with less danger of shattering during the drilling operation.

The advantages associated with the all-regenerated cellulose filledcompositions are, to a large extent, present in the new moldingcompositions, such as greater translucency and colorability, greaterdensity and lower bulk factor, improved flow in the hopper used inconjunction with the molding device, more rapid grinding, and theobtention of suflicient uniformity of distribution when the compositionsare ground to comparatively large particle size so that grinding toextremely small particle size is unnecessary.

The following examples will serve to illustrate specific, representativeembodiments of the invention, it being understood that these specificexamples are not intended to be limitative.

Example I erated cellulose (chipped cellophane) and 210 parts ofpurified cellulose pulp is mixed in a shredder at a temperature between25 C. and C. for one hour during which reaction occurs with formation ofa resin-forming condensate, and thorough impregnation of thecellophanealpha-cellulose filler with the condensate is effected. Themixture is placed in a circulating air drier at 60-80 C.

' and dried to the desired condition of flow as determinedexperimentally in a suitable mold. During the drying,

further reaction occurs between the urea and formalde- The driedmaterial is then reduced to the desired particle size and density bygrinding it in a ball mill, and

' during such grinding zinc stearate, a coloring material,

and a curing catalyst is incorporated with it.

' except that the filler comprising the mixture of regen- Example IIIThe steps of Example I were repeated except that the 390 parts ofregenerated cellulose were replaced by 350 parts of a water-insoluble,alkali-soluble hydroxyethyl cellulose ether having 1.2 hydroxyethylgroups per anhydroglucose unit.

Example IV The procedure of Example II was followed except that the 390parts of regenerated cellulose were replaced by 410 parts of awater-insoluble but alkali-soluble methyl cellulose having 0.8 methylgroups per anhydroglucose unit.

Example V A resin-forming condensate is prepared from 600 parts byweight of melamine and 1050 parts by Weight of formalin (37%formaldehyde) neutralized with triethanolamine or other suitable base byreacting at the temperature of a boiling water bath until a samplecooled to room temperature and diluted with an equal volume of watershows a precipitate. Two hundred parts of chipped cellophane, 150 partsof a water-insoluble, alkali-soluble hydroxyethyl cellulose, and 100parts of alpha-cellulose are then added and the whole mass is mixed in ashredder for one-half hour to effect thorough impregnation. The mixtureis placed in a circulating air drier at C. and dried. The dried materialis then powdered in a ball mill in which small proportions of a zincstearate, a pigment, and a latent curing catalyst are introduced.

By using dyed or pigmented cellophane, and/or by blending or mixingcompositions of dissimilar particle size and flow characteristics, awide range of artistic and decorative effects may be achieved, frombright, nearly transparent, solid colors to mottles and variegations ina translucent medium.

An additional advantage of the molding compositions of the invention isthat the powders obtained by grinding the dried impregnated mass in anordinary ball mill or the like have, prior to densification bygranulation, a low bulk factor (volume of composition/volume of moldedobjects), which facilitates molding. The density of the powder prior togranulation is close to the density of granulated powders containing afiller consisting of alphacellulose, so that, for many purposes, theconventional I step of granulating the powder obtained initially may beeliminated. However, the compositions may be granulated, if desired.

Other thermosetting aminoplast resin-forming condensates may besubstituted for all or part of the resins employed in the examples, suchas the resins obtained by reacting an aldehyde, e. g., formaldehyde,acetaldehyde, benzaldehyde, furfuraldehyde, etc. with the following:thiourea, the reaction products obtained by heating and decomposingdicyandiamide, melamine, or other amino triazines, etc. The moldingcomposition may also contain mixed resins, e. g.,urea-melamine-formaldehyde resins, urea-thiourea-formaldehyde resins,etc. The molar ratios between the aldehyde and the other component orcomponents may vary widely and the resins can be prepared by any of themethods known in the art.

The filler content, the composition of the resin (mole ratio of theresin-forming constituents and proportion of minor ingredients) and theprocessing conditions may be varied. However, in general, thecomposition will comprise from 60 to 70, preferably about 65, parts ofresinforming component to from 30 to 40, preferably about 35, parts offiller.

The regenerated cellulose or water-insoluble, alkalisoluble celluloseether may be used in any form. For example, they may be in the form offragments or chips of sheet or film material, in the form of fibers orthreads, for example, scrap or waste from rayon manufacture in the caseof regenerated cellulose, or in the form of an unshaped regeneratedcellulose gel which has been dried and reduced to particulate conditionand is of non-cellular character. Instead of using cellophane or thecellulose ether in the form of chips, the chips may be disintegrated toa powder prior to impregnating them with a resinforming precondensate orthe liquid, resin-forming constituents.

The molding compositions of the invention may be used in moldingarticles of all kinds, including buttons, novelty articles, toys,ornamental articles, packaging cartons or boxes such as ring boxes,watch boxes, and jewelry boxes, generally, etc.

Since variations and modifications may be made in practicing theinvention, without departing from the spirit thereof, it is to beunderstood that the invention is not to be limited except as defined inthe appended claims.

I claim:

1. A molding composition which comprises (1) from 30 to 40 parts of afiller comprising a mixture of from to 50 percent of alpha-cellulose andfrom 50 to 90 percent of a substance selected from the group consistingof regenerated cellulose, and water-insoluble alkali-soluble celluloseethers, and (2) from 60 to 70 parts of a dry, fusible, thermosettingresin-forming material consisting of an aminoplast condensate of analdehyde and a compound selected from the group consisting of urea,thiourea, melamine and mixtures of the compounds in said group.

2. A molding composition as defined in claim 1 wherein the aminoplast isa urea-formaldehyde resin-forming condensate.

3. A molding composition as defined in claim 1 wherein the aminoplast isa melamine-formaldehyde resinforming condensate.

4. A molding composition as defined in claim 1 wherein the aminoplast isa urea-melamine-formaldehyde resinforming condensate.

5. A molding composition as in claim 1 wherein the filler comprises amixture of alpha-cellulose and a waterinsoluble, alkali-solublehydroxyethyl cellulose ether.

6. A molding composition as in claim 1 wherein the filler comprises amixture of alpha-cellulose and a waterinsoluble, alkali-soluble methylcellulose ether.

7. A molding composition which comprises (1) from 30 to 40 parts of afiller comprising a mixture of from 50 to 90 percent of regeneratedcellulose and from 10 to 50 percent of alpha-cellulose, and (2) from 60to 70 parts of a dry, fusible, thermosetting resin-forming materialconsisting of an aminoplast condensate of an aldehyde and a compoundselected from the group consisting of urea, thiourea, melamine andmixtures of the compounds in said group, said resin-forming materialbeing intimately combined with said filler.

8. A molding composition as in claim 7, wherein the filler isimpregnated with a urea-formaldehyde resin condensate.

9. A molding composition as in claim 7, wherein the filler isimpregnated with a melamine-formaldehyde resin condensate.

10. A molding composition as in claim 7, wherein the filler isimpregnated with a melamine-urea-formaldehyde resin condensate.

11. A molding composition containing a filler comprising a mixture ofabout 65 parts of regenerated cellulose and about 35 parts ofalpha-cellulose, said filler being impregnated with a urea-formaldehyderesin-forming condensate.

12. A molding composition containing a filler comprising a mixture ofabout 65 parts of regenerated cellulose and about 35 parts ofalpha-cellulose, said filler being impregnated with amelamine-formaldehyde resin-forming condensate.

13. A molding composition containing a filler comprising a mixture ofabout parts of regenerated cellulose and about 35 parts ofalpha-cellulose, said filler being impregnated with arnelamine-urea-formaldehyde resinforming condensate.

14. A method for making molded objects which comprises intimatelycombining 30 to 40 parts of a filler comprising a mixture of from 10 to50 percent of alpha-cellulose and from 50 to 90 percent of a substanceselected from the group consisting of regenerated cellulose andwater-insoluble, alkali-soluble cellulose ethers with a liquidcomprising 60 to parts of a thermosetting resinforrning materialconsisting of an aminoplast condensate of an aldehyde and a compoundselected from the group consisting of urea, thiourea and melamine toobtain a. mass comprising the filler impregnated with the liquid andsubstantially free from liquid which is not intimately combined with thefiller, drying the mass to obtain a composition comprising the fillerimpregnated with the resinforming material which is in a dry, fusiblestate, and molding the composition under heat and pressure.

15. A method as in claim 14, wherein the filler comprises a mixture ofalpha-cellulose and regenerated cellulose.

16. A method as in claim 14, wherein the filler comprises a mixture ofalpha-cellulose and a water-insoluble, alkali-soluble hydroxyethylcellulose ether.

17. In a molding composition containing from 60 to 70 parts of a dry,fusible, thermosetting resin-forming aminoplast condensate as a binder,said condensate consisting of a condensate of an aldehyde and a compoundselected from the group consisting of urea, thiourea, melamine andmixtures of these compounds, and from 30 to 40 parts of a fillerintimately mixed with said hinder, the improvement which comprises afiller for the molding composition comprising a mixture containing from10 to 50 percent of alpha-cellulose and from 50 to percent of asubstance selected from the group consisting of regenerated cellulose,and water-insoluble, alkali-soluble cellulose ethers.

References (Iited in the file of this patent UNITED STATES PATENTS1,721,742 Nash July 23, 1929 2,322,566 DAlelio June 22, 1943 2,367,275Haney et a1 Jan. 16, 1945 2,665,261 Baker Jan. 5, 1954

1. A MOLDING COMPOSITION WHICH COMPRISES (1) FROM 30 TO 40 PARTS OF AFILLER COMPRISING A MIXTURE OF FROM 10 TO 50 PERCENT OF ALPHA-CELLULOSEAND FROM 50 TO 90 PERCENT OF A SUBSTANCE SELECTED FROM THE GROUPCONSISTING OF REGENERATED CELLULOSE, AND WATER-INSOLUBLE ALKALI-SOLUBLECELLULOSE ETHERS, AND (2) FROM 60 TO 70 PARTS OF A DRY FUSIBLE,THERMOSETTING RESIN-FORMING MATERIAL CONSISTING OF AN AMINOPLASTCONDENSATE OF AN ALDEHYDE AND A COMPOUND SELECTED FROM THE GROUPCONSISTING OF UREA, THIOUREA, MELAMINE AND MIXTURES OF THE COMPOUNDS INSAID GROUP.